I am using a spam prevention mod that also allows me to check users already registered, this means I am going through all registered user accounts in search of registered spammers to clean it all up, the criteria is simple: check a database, if the username, ip, mail or display name are in it, it marks them as possible spammers.

If only the username or IP coincides I might not delete it, but if two or more do then I am removing the account entirely. What does that mean?

If your account was removed or you are a lurker and don't want  that to ever happen to you, then i advise you to post at least once in the forum, since users with posts are checked for them before being removed.

As of now, I removed more than 100 users from the site.

This being the first time I have been on this site, (great one too! IMHO) I can understand why you are doing this.  I will admit that I am guilty of joining a site and going through it and finding nothing of interest, I never return.  But I searched for a Midnight campaign site because I saw the Midnight Chronicles movie for the first time last night and was very impressed with the setting.  The film really conveyed the feel of the world and as I was watching the credits at the end I spotted the Fantasy Flight Games plug...  So here I am.  I will be returning on a regular basis for the purpose of including parts of this world into mine.

Lurker emerges from swamp, looks around, and submerges